Salicylaldehyde, 796 table

LDPE or HDPE extracts has been determined colorimet-rically at 430 nm by oxidation with H202 in the presence of H2S04 [66]. p-Phenylenediamine derivatives such as Flexzone 3C, used as antiozonants in rubber products, have been determined colorimetrically after oxidation to the corresponding Wurster salts [67]. A wide range of amine AOs in polyolefins has been determined by the p-nitroaniline spectrophotometric procedure [68]. Monoethanolamine (MEA) in a slip agent in PE film has been determined as a salicylaldehyde derivative by spectrophotometric quantification at 385 nm [69]. Table 5.6 contains additional examples of the use of 1JV/VIS spectrophotometry for the determination of additives in polymers. 

Table 5 summarizes the reactions of isoprene with aromatic aldehydes and unsaturated aldehydes. Salicylaldehyde provides the expected product as a cyclic boric ester derivative and shows apparently lower stereoselectivity, giving a mixture of 1,3-anti and 1,3-syn isomers in a ratio of 6 1 (run 1, Table 5). 2-Furfural reacts as usual and provides a 1,3-anti isomer as a single diastereomer in good yield (run 2). Unsaturated aldehydes, irrespective of their substitution patterns, undergo homoallylation selectively with excellent 1,3-anti selectivity, the geometry of the double bond of the starting aldehydes remaining intact (runs 3-5). 1,2-Addition to unsaturated aldehyde takes place selectively and no 1,4-addition is observed.

The Fe(III) complexes of R-substituted salicylaldehyde thiosemicarbazone (R-thsa2- Fig. 6) are among the most studied spin crossover materials of this family. The crystal structures of several of them have been determined at various temperatures. The iron-donor atom distances are compiled in Table 2. The Fe(III) ion is in a distorted FeS2N202 octahedron formed by two thiosemicarbazone ligands, which are geometrically arranged in such a way that the S and O atoms are located in cis positions, whereas the N atoms occupy trans positions, i.e. each tridentate molecule coordinates in an equatorial plane [101]. 

Table 2 Fe-donor atom bond lengths for various (cation+)[Fe(ligand2 )2]-nH20 compounds of R-salicylaldehyde thiosemicarbazone (R-thsa2-) [101]... 

Very early in the study of photosensitization it was discovered that salicylaldehyde, 2,4-dihydroxybenzophenone, and 2-hydroxy-4-methoxy-benzophenone do not sensitize piperylene isomerization, indicating that enolization is much faster than quenching by the diene.37 Later it was shown that 2-hydroxybenzophenone would sensitize the dimerization of isoprene in concentrated solution, but that the reaction was much less efficient than when benzophenone was used as a sensitizer (Table I).36... 

Table 40 Some Oxovanadium(IY) Complexes Derived from Salicylaldehyde or Substituted Salicylalde-hyde with 2-Aminoethanethiol (83), 3-Aminothiophenol (84) or 2-Aminothiophenol (86) (on reflux)...

Table 7 Synthesis of Coumarins by a Knoevenagel Reaction on Salicylaldehyde...

Most nickel(II) complexes with the various Schiff bases derived from salicylaldehyde and different amines have usually been easily prepared by three general methods (i) the reaction of a nickel(II) salt, usually hydrated nickel(II) acetate, with the preformed Schiff base using water, EtOH, MeOH or their mixtures as reaction medium (ii) the condensation reaction of bis(salicylaldehydato)nickel(II) with the appropriate amine in refluxing EtOH or H20/EtOH mixture (iii) the template reaction of the aldehyde with the appropriate amine in the presence of a nickel salt. In Table 97 the formulas, synthetic methods and some physicochemical properties for a number of nickel(II) salicylaldiminato complexes are reported. Examples of dinuclear complexes formed with Schiff bases are specifically reported in Section 50.5.8.5. 

Table 97 Nickel(ll) Complexes with Bi- and Poly-dentate Schiff Base Ligands Derived from Salicylaldehyde or Related Aldehydes and Various Amines... 

The most studied bidentate Schiff bases containing an N,0 donor set are those derived from substituted salicylaldehyde derivatives, since they have been widely used as ligands for many transition metal complexes.73 They have also been investigated extensively because of their meso-morphism in the solid state. Those which have been structurally characterized are collected in Table 7 together with some structural parameters of interest. 

Salicylaldehyde has been condensed with many primary amines to yield bidentate N—O ligands. Such ligands react with MnIU acetate dihydrate to give compounds of stoichiometries Mn(L)3 or Mn(L)2(X) (where HL = (227) X = Cl, Br, OH or OAc) examples are listed in Table 50. 

A 13C-NMR spectroscopic study in solution of the tautomers of several anils derived from salicylaldehyde and from 2-hydroxynaphthalene-l-carbaldehyde having the same amino part (141-145, Scheme 17) has been reported.82 Variable-temperature NMR spectroscopy and comparison with appropriate models show that while salicylideneanilines exist as phenolic tautomers, naphthylidene-anilines exist as equilibrium mixtures containing appreciable amounts ofboth enol and keto tautomers, the latter being slightly predominant (Table 9). In fact, there is a negligible shift in the equilibrium on changing the electronic effect of the R substituent. 

Enantioselection can be controlled much more effectively with the appropriate chiral copper, rhodium, and cobalt catalyst.The first major breakthrough in this area was achieved by copper complexes with chiral salicylaldimine ligands that were obtained from salicylaldehyde and amino alcohols derived from a-amino acids (Aratani catalysts ). With bulky diazo esters, both the diastereoselectivity (transicis ratio) and the enantioselectivity can be increased. These facts have been used, inter alia, for the diastereo- and enantioselective synthesis of chrysan-themic and permethrinic acids which are components of pyrethroid insecticides (Table 10). 0-Trimethylsilyl enols can also be cyclopropanated enantioselectively with alkyl diazoacetates in the presence of Aratani catalysts. In detailed studies,the influence of various parameters, such as metal ligands in the catalyst, catalyst concentration, solvent, and alkene structure, on the enantioselectivity has been recorded. Enantiomeric excesses of up to 88% were obtained with catalyst 7 (R = Bz = 2-MeOCgH4). 

Several examples of the present aldol reactions of silyl enol ethers with aldehydes in water-ethanol-toluene are listed in Table 6.3-Pyridinecarboxaldehyde as well as 2-pyridinecarboxaldehyde, salicylaldehyde, and formaldehyde water... 

Several examples of the present aldol reactions of silyl enol ethers with aldehydes in water-ethanol-toluene are summarized in table 6. 3-Pyridinecarboxaldehyde as well as 2-pyiidinecarboxaldehyde, salicylaldehyde, and formaldehyde-water solution worked well. As for silyl enol ethers, not only ketone enol ethers but also silyl enolates derived from thioesters were used. In every case, the adducts were obtained in high yields in the presence of 10mol% Yb(OTf)3. 

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